1. Technical Field
The present invention is directed toward battery chargers, and more particularly toward chargers usable with different batteries for mobile communication units which may be charged with different currents.
2. Background Art
Mobile communication units such as cellular telephones for the most part are powered by portable batteries which are connected to the units and which must be periodically recharged.
In many cases, battery chargers are provided in which the battery may be taken from the phone and charged. In such cases, however, the phone is then either taken out of service during charging or a second battery must be available to use while the first is being charged.
Alternately, some battery chargers are adapted to charge the battery while it is in the phone. Such chargers allow the phone to be available for use while its battery is charging. Typically, the charging may be accomplished by connecting a two-wire charger output to a two-wire charging input on the phone.
However, as a current example, 3 V platform phones now in the market may be used with different batteries which may be charged at different rates. Small batteries (e.g., 450 mAh batteries) usable with such phones can be safely charged by approximately 700 mAh output from the charger. Larger batteries may be safely charged using greater output (e.g., 900 mAh) but using such a greater output to charge the small batteries can damage the small batteries. As a result, to safely charge batteries in such phones, it is necessary to charge at only 700 mAh output maximum (to ensure that a small battery not be damaged if that is what is in the phone), which unfortunately means that the larger batteries are not charged as quickly as they could be. That is, while the larger batteries could be most quickly charged by use of chargers having a greater output such as 900 mAh (whether such output is all that is provided by the charger or one of several which may be manually selected), if the phone is inadvertently or unknowingly placed in a charger with such a greater output while the phone has a smaller battery, the battery would be damaged or destroyed. Further, while an extra lead (e.g., third-wire communication circuit) could be provided to signal from the phone to the charger what type of battery is being charged for automatic selection of the appropriate output, such an extra circuit would be incompatible with most other accessory system connectors which only allow for a two-wire interface at the charger interface connector.
Further, in many cases when the phone is in use while in a charger, as is common when used in a vehicle charger, the phone draws more current when transmitting than the typical charger puts out. In case the phone is put in such a charger when its battery is almost discharged and then begun to be used, the continued gradual draining of the battery during subsequent transmitting (when current from the charger must be supplemented by current from the battery) could result in a call being dropped, with the battery then so discharged that it will take some time for sufficient power to be restored to the battery to enable the user to reconnect the dropped call.
The present invention is directed toward overcoming one or more of the problems set forth above.